The present invention relates to filtration systems and more particularly, to industrial filtration systems using reverse osmosis units.
The use of reverse osmosis systems is well known in the art. These systems are used in the production of potable water from sea water and in industrial operations to produce high quality water for specialized purposes such as boiler makeup, use in printing presses, semi conductor manufacture, and in pharmaceuticals and in various other industries. It is known that reverse osmosis systems can produce water having low levels of suspended and total dissolved solids.
In the operation of reverse osmosis systems, the input liquid is divided into two output streams--a permeate stream which is substantially free of the dissolved substance and a concentrate stream which contains the majority of the substance to be removed. Reverse osmosis systems utilize a semi-permeable membrane with the input stream being fed at a pressure substantially above the osmotic pressure of the feed solution. When it is fed across the membrane, water molecules preferentially pass through the membrane with a very limited amount of the dissolved substances also passing through the membrane, depending upon the type of membrane and operation of the system.
In many industrial operations, a portion of the concentrate stream is recycled back to the input. The reason for this is that reverse osmosis systems are not efficient enough to concentrate the undesirable product to a sufficient extent to merely discharge the concentrate stream to drain unless one is dealing with an unlimited supply of water and does not have problems in discharging the concentrate--e.g. a desalination. In a typical industrial plant, one must minimize the discharge of water which typically goes to drain, both for pollution control purposes and to minimize use of water.
To overcome the above, most reverse osmosis systems used for industrial purposes operate in a manner so as to fix a predetermined amount of the concentrate which is recycled back to the inlet. While this does reduce the amount of water discharged, inherently it becomes an inefficient system since one must err on the side of safety and not discharge more than one is certain will not result in contamination of the permeate stream. Typically, systems recycle approximately 75% of their concentrate stream back to the inlet.
It is an object of the present invention to provide a reverse osmosis system which minimizes the amount of liquid discharged to the drain.
It is a further object of the present invention to provide a reverse osmosis system which automatically functions to provide maximum efficiency in the removal of unwanted material from the liquid being treated.